When killing is the law and showing mercy is a crime, how guilty are those who follow the orders of the ruling authorities?

This question lies at the heart of Thierry Cruvellier’s recent book “Master of Confessions,” which details the trial of Comrade Duch, a former math teacher responsible for the torture and death of some 12,000 people in Cambodia in the 1970s.

The book explores the humanity of a man who tried to impress his bosses and excel at his job. It just so happens that his bosses were the Khmer Rouge, and his job was to manage the S-21 prison, where suspected “traitors” were tortured and killed. By a certain measure, he was extremely good at what he did. Almost every prisoner confessed. Almost every prisoner supplied the names of more “traitors,” who were subsequently arrested and killed. Duch, an enthusiastic bureaucrat, prided himself on attention to detail. He ran his death mill so skillfully that his own meticulous notes became the most damning evidence against him.

“Back then, I believed in what I was doing,” Duch told the judges. “But as I look back now, it makes me shudder.”

It was my first steady job as a journalist. I had been sent by a far-away boss, and knew little about Rwanda when I arrived. Cruvellier, a cantankerous but warm-hearted Frenchman, had come of his own accord. He published a bimonthly newsletter which occasionally included scoops so explosive that prosecutors were forced to change their tactics or drop charges. He knew all there was to know about the court. Luckily, he shared his knowledge with me. (Full disclosure: He’s still a friend.)

For two years, we watched the trial of Rwandan governor Clément Kayishema and his side kick, Obed Ruzindana, who were accused of killing people who’d hidden in churches and fields. The accused wore tailored suits and headphones to understand the English-speaking judges. I searched their faces daily for signs of regret.

Cruvellier’s first book “Court of Remorse” chronicled the Rwandan trials. Then he went on to become the world’s most dedicated genocide trial junkie. He’s covered more trials over more years in more countries than any journalist I know of. From Rwanda and The Hague, to Sierra Leone and, finally, Cambodia.

After every trial, he asked the question: Who is this expensive international justice for? The peasant farmers who give their testimonies, only to return home to poverty and meals less delicious than what the killers eat in UN jails? Was it for the “international community,” which needed absolution for its failure to stop the killings? Or for killers to get one last shot at forgiveness?

Perhaps, at the end of the day, it’s for history. We bear witness and memorize the patterns so that we can recognize them when we see them again.

Somehow, the tiniest details matter. It matters whether Kayishema and Duch enjoyed their jobs. It matters whether they spared anyone — an old friend? A sister? — who had been slated for slaughter. Did they believe they were doing what was right for their country? If so, does that make them any less guilty?

At one point during Duch’s trial, he tells the judges that if he had refused to run S-21, “someone else would have taken my place.”

He’s right. In the face of overwhelming pressure and the constant fear of death, very few of us would refuse. But every genocide has its resisters. In Rwanda, the Muslim community protected its Tutsis. In Cambodia, some prisoners died of torture before giving up anyone else’s name. We all want to think that we’d be strong enough to do that. But precious few of us are.

That’s why it is so crucial that the governments we build are just. When you set out to study extraordinary acts of evil, you discover how easily evil can become the norm, and what a precarious outlier goodness can be.

After all these years of examining genocide, that’s the biggest take-away for Cruvellier.

“It has really made me wonder about those who resist,” he said. “To me, they are the real mysteries.”

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